JPS6229636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system, and particularly to a fuel supply system suitable for use in a multi-cylinder internal combustion engine.

In general, fuel supply systems for multi-cylinder internal combustion engines include two methods: a method in which a solenoid valve provided for each cylinder is controlled ON-OFF and metered independently, and a method in which fuel from a single metering valve is divided and distributed to each cylinder. method (for example, JP-A-Sho
No. 55-29096, Japanese Unexamined Patent Publication No. 52-11812). Both of these methods tend to generate fuel vapor bubbles in the fuel piping, and to prevent this, it is necessary to reduce the fuel pressure in the piping.
It has to be maintained at 2.0 kg/cm ² or more, and the driving horsepower of the fuel pump is greater than that of a carburetor, which has the disadvantage of increasing fuel consumption. Furthermore, the former independent metering method requires the provision of highly accurate electromagnetic valves in order to equalize the amount of fuel in each cylinder, which has the disadvantage of increasing costs.

The object of the present invention is to provide a distribution type fuel supply device that can prevent the generation of fuel vapor bubbles in fuel piping, reduce the fuel pressure to about 0.6 kg/cm ² , and reduce the driving horsepower of the fuel pump. It is about providing.

The gist of the present invention is as follows. In other words, in a known example of a conventional distribution system, JP-A No. 55-29096, the fuel is branched downstream of the constant pressure valve, and a fixed orifice is installed at the tip of the branch pipe to separate the flow, so the fuel flow rate is small during idling operation. Flow in the branch pipe in the area〓〓〓〓〓
It was found that the amount and pressure became small and it was difficult to prevent the generation of steam bubbles. In the above-mentioned known example, a second constant pressure valve and a second branch pipe are added, and the second constant pressure valve is operated in a region where the flow rate is large;
By diverting some of the fuel through branch pipes,
A method for relatively suppressing a drop in the flow rate and pressure in the first branch pipe is also disclosed, but when the engine is stopped and the flow rate is zero, the pressure in the pipe becomes atmospheric pressure, suppressing the generation of steam bubbles. Can not do it. Due to the generation of vapor bubbles, some of the fuel in the pipe is forced out of the orifice and enters the intake pipe, making the air-fuel mixture in the intake pipe too rich, further making it difficult to restart the engine.

A common way to avoid this is to install a check valve at the end of the fixed orifice to reduce the pressure and
This is a method to prevent fuel leakage. However, if you install a check valve at the tip and try to maintain the pressure inside the branch pipe at a high pressure, the flow rate characteristics of the check valve will affect the diversion ratio, so a flow divider such as that disclosed in JP-A-52-118125 is used. It is necessary to provide an equal amount of divided flow to each cylinder. In addition, since fuel remains in the branch pipe when the engine is stopped, it is necessary to maintain a pressure of about 2.0 kg/cm ² to prevent the generation of steam bubbles, and check valves are installed to prevent leaks. A high degree of accuracy is required.

In the process of conducting various experiments on the above two known examples, the latter method maintains the fuel pressure at a high pressure, and when the fuel pressure is reduced to about 0.6 Kg/ ^cm2 , the generation of fuel vapor bubbles in the branch pipe is prevented. It turned out to be difficult. Due to the generation of vapor bubbles, the fuel in the branch pipe becomes empty, and during restart, fuel is not supplied to the engine while the branch pipe is filled with fuel, and restarting of the engine is significantly inhibited. This problem can be resolved by reducing the diameter of the branch pipe, but reducing the diameter of the branch pipe increases the pressure loss.
It is difficult to cover the maximum flow rate at a pressure of 0.6Kg/cm ² . For this reason, a method of providing a second branch pipe is considered, but it requires check valves equal to the number of branch pipes, and the fuel in the second branch pipe remains, so the total amount of fuel in the branch pipe is did not decrease, and therefore it was found that the problem essentially could not be resolved.

In the former known example having the second branch pipe, the above-mentioned problems are the same, and since there is no check valve, the fuel pressure is low, and the generation of fuel vapor bubbles is also severe. However, during the course of the experiment, it was found that the above problem could be resolved by draining the fuel in the branch pipe beforehand when the engine was stopped. However, if the fuel is empty, it will take time to restart as mentioned above. This problem can be avoided by providing a means for filling the branch pipe with fuel when starting the engine.

Therefore, the present invention prevents the generation of fuel vapor bubbles in the fuel piping by providing means for sucking fuel into the branch pipe that divides the fuel into each cylinder, and means for filling the branch pipe with fuel. The idea is to lower the fuel pressure to about 0.6 kg/cm ² and reduce the driving horsepower of the fuel pump.

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the invention.

The fuel supply device includes a fuel pump section 1, a fuel metering section 2, a flow dividing section 3, and an air metering section 4.

The fuel pump section 1 is as follows. That is,
The pressure is 0.6 with centrifugal and vortex fuel pump 10.
Kg/ ^cm2 , and through the check valve 11,
Fuel is pumped into the pressure regulator 12. The pressure in the lower chamber 13 of the regulator 12 is maintained constant, and excess fuel returns to the fuel tank 15 through the return pipe 14. Steam bubbles are also discharged from the return pipe 14. Further, the fuel metering section 2 is as follows. That is, one end of the pipe 21 is connected to the lower chamber 13 of the regulator 12, and the other end of the pipe 21 is provided with a metering valve 23,
The downstream side of the metering valve 23 is connected via a pipe 22 to a lower chamber 25 of a pressure regulator 24 . The upper chamber of the pressure regulator 24 is connected via a pipe 26 to
It is connected to the pipe 21. This pressure regulator 2
4, the pressure difference before and after the metering valve 23 is 0.1
Maintained at around Kg/ ^cm2 . The metering valve 23 is a normal needle valve or a slit valve, and the flow path area changes depending on the stroke.
That is, the scroll controls the fuel flow rate through the tube 22. The stroke is controlled by a mechanical quantity conversion means 28 such as a proportional solenoid connected to the metering valve 23 or a pulse motor in accordance with commands from the microcomputer 27. Signals such as engine rotational speed and accelerator pedal opening are input to the microcomputer 27. This results in
An appropriate amount of fuel flows through the pipe 22 according to the engine condition.
Ru. The metering valve 23 may be an intermittent electromagnetic solenoid valve. In this case, the flow rate is controlled by the valve opening time width. The flow rate varies from 1 to 50/h, which is the total flow rate of the engine. The metering valve 23 may be a metering means such as a volumetric pump.

Further, the flow dividing section 3 is as follows. That is,
A pipe 31 is connected to the pressure regulator 24 . A branch pipe 32 and a branch pipe 33 are branched from the pipe 31. An orifice 3 is installed at the tip of the branch pipe 32.
4a and an orifice 34b are attached.
Orifices 35a and 35b are provided at the tip of the branch pipe 33.
is installed. Orifice 34a, 34
b, 35a, and 35b have the same diameter of about 0.5 mm, and the fuel flowing out from each orifice flows into the 1st cylinder, 2nd cylinder, 3rd cylinder, respectively.
It is supplied to the fourth cylinder. The flow rate of the pipe 31 is equally distributed to each cylinder by an orifice. The pipe 31 is provided with a valve 36, and when the flow rate of the pipe 31 increases, the branch pipes 38 and 39 are opened. The electromagnetic solenoid 37 is driven by the microcomputer 27 to pull down the valve 36. During this lowering operation, the branch pipes 38 and 39 are filled with fuel in the portion indicated by A below the valve 36. When the valve 36 is pulled down to position B, the branch pipes 38 and 39 are opened and the orifices 34c and 34 are opened.
d, 35c, and 35d, respectively, the first cylinder,
Fuel is supplied to the second, third, and fourth cylinders. In this state, when the overall flow rate decreases, the valve 36 returns to the position A, draws back the fuel in the branch pipes 38 and 39, and fills the part A. Therefore, the fuel in the branch pipes 38 and 39 becomes empty,
The generation of fuel vapor bubbles when the engine is stopped is prevented.

Further, the air measuring section 4 is as follows. That is, the throttle valve 4 provided in the intake pipe 43 of the engine
1 is rotated by a servo motor 42. A signal from an air flow meter 44 attached to a part of the intake pipe 43 is input to the microcomputer 27, and the servo motor 42 is driven so that the air flow rate reaches a set value, thereby opening and closing the throttle valve 41.

FIG. 2 shows a detailed view of the flow dividing section 3.

In the figure, pipe 31 is connected to flow dividers 59, 60, 61
It is connected to the. Now, valve 5 of flow divider 59
When 3 is pulled down, the branch pipes 32 and 33 are filled with fuel, and the valve 53 is lowered to the position 53a, so the branch pipes 32 and 33 are connected to the pipe 31.
The fuel in the pipe 31 is equally distributed to each cylinder from orifices 34a, 34b, etc. Here, other orifices are omitted. When the flow rate increases, the valve 54 of the flow divider 60 is pulled down, and the branch pipes 38,
39 is filled with fuel, and fuel is supplied to each cylinder from the orifice at the tip. When the flow rate increases further, the valve 55 of the flow divider 61 is pulled down, and after the branch pipes 51 and 52 are filled with fuel, fuel is supplied to each cylinder from the orifice at the tip. In this way, as the fuel flow rate increases, the entire opening area of the orifice at the tip increases.
As shown in Figure 3, the pressure can be suppressed to about 0.5Kg/cm ² . In Figure 3, the shunt 6 at _Q1
0, the shunt 61 operates at _Q2 . When the flow rate decreases, the valve 55 is first pulled up to empty the fuel in the branch pipes 51 and 52, and then the valve 54 is pulled up.
is pulled up to empty the fuel in the branch pipes 38 and 39, and finally, when the engine is stopped, the valve 53 is pulled up to empty the fuel in the branch pipes 32 and 33. Therefore, when the engine is stopped, there is no fuel in the branch pipe, and no steam bubbles are generated even if it is heated by the heat of the engine. Valves 53, 54, 55 are controlled by microcomputer 27 by solenoids 56, 57, 58. Q ₁ , Q ₂ in Figure 3
When the valves 54 and 55 operate at this point, the valves 54 and 55 should have some hysteresis characteristics.
Prevents ON/OFF operation. As can be seen from the system of FIG.
As a result of this operation, the differential pressure of the metering valve 23 is maintained constant, so the fuel flow rate does not change.

Next, the operation of the pressure regulator 24 will be explained. Now, when the pressure P ₁ in the tube 22 increases, the diaphragm 70 of the pressure regulator 24 in FIG.
push up. Therefore, the pressure P ₁ in the tube 22 decreases and maintains the pressure P ₁ in the tube 22 constant. Figure 4 shows the relationship between flow rate Q and pressure _P1 . Here, tube 31
As the pressure P ₂ increases with respect to the flow rate Q as shown in Figure 4, the flow rate of fuel passing through the gap 71 at the bottom of the diaphragm 70 decreases, and since the same flow rate is processed, the gap 71 increases. . In other words, da〓〓〓〓〓
It is necessary to pull the earphragm 70 higher. That is, P ₁ is raised to P _1a . However, in the present invention, as shown in FIG.
Since the increase in pressure P ₂ is suppressed, the change in P _1a is small. In the configuration shown in FIG. 1, when the metering valve 23 is suddenly disconnected, the flow rate of the pipe 22 becomes zero, and the gap 7
1 becomes zero. The pressure of 0.6 kg/cm ² from the tube 26 is applied to the diaphragm 70 from above, and the pressure from the spring 72 is applied to the diaphragm 70 from above.
0.1Kg/cm ² is acting from below. Gap 71
When the fuel in the pipe 22 leaks from the gap 71, the downward force increases and prevents the fuel from leaking from the gap 71. When the engine is stopped, the valves 53, 54, and 55 close off the outlet of the pipe 31. Therefore, when the gap 71 is leaking, the pressure between the pipe 22 and the pipe 31 is maintained at an intermediate value. In this way, even if the pressure regulator 24 leaks to some extent,
Fuel will not leak and be supplied to the engine.

Next, the treatment of steam bubbles in the piping will be explained.

In FIG. 1, vapor bubbles generated in the pipes 21 and 26 can be easily discharged to the upper part of the pressure regulator 12 by providing the pressure regulator 12 at the upper part. The fuel can be easily discharged through the return pipe 14 at the same time as the fuel pump 10 is started, and problems caused by fuel vapor bubbles will not occur.
Steam bubbles in tube 22 are blocked by metering valve 23;
It is difficult to discharge to the regulator 12 side. The steam bubbles in the pipe 22 are discharged to the pressure regulator 24 side as shown in FIG. Steam bubbles discharged to the pressure regulator 24 side
It accumulates in the left chamber of the diaphragm 70. Steam bubbles in the tube 31 also accumulate in the left chamber of the diaphragm 70. The vapor bubbles pass through valve 53, branch pipe 32, and are discharged from orifice 34a. During operation, the valve 53 is sucked to the left by the solenoid 56, and the branch pipe 32 is filled with fuel from section A. The pipe 31 and the branch pipe 32 are connected, and the flow rate of the pipe 31 is controlled by the orifice 34a, etc. It is distributed to each cylinder through When the engine is stopped, the fuel in the branch pipe 32 is drawn back to section A as described above. Although the fuel in this part A boils when heated, it is not discharged from the orifice 34a because the diameter of the branch pipe is small, about 2 mm. Also, since it is not exposed to air, evaporation loss is minimal. In the configuration shown in FIG. 5, it is the tube 31 that generates the most significant steam bubbles. This is discharged to the outside through the bleed hole 100.

Another embodiment of the flow divider is shown in FIG.

In the figure, a lever 201 is attached to a throttle valve 41 that throttles the amount of air in an engine 200.
When the throttle valve 41 rotates, the lever 201 moves, and as shown in FIG.
Move 02,203. Hook the claw of the valve stem 204 of the valve 53 with the claw of the member 202, and
Attach the pawl of the valve stem 205 of the valve 54 with the pawl 03. In this way, depending on the opening degree of the throttle valve 41, first the valve 53 is operated, and then the valve 54 is operated. In this case, the solenoids 57 and 58 shown in FIG. 2 become unnecessary. FIG. 8 is a modification of FIG. 6, in which diaphragms 255 and 256 are used instead of the piston valve to take in and take out fuel. The suction negative pressure is transferred from the pipe 257 to the diaphragm 25.
5,256. When the suction negative pressure becomes smaller, the diaphragms 255 and 256 move to the right,
Open valves 258 and 259 one after another. FIG. 9 shows another embodiment in which when the fuel flow rate through the pipe 31 is small,
The pressure regulator 301 operates, and the branch pipes 32,
33 to distribute fuel to each cylinder. When the flow rate increases, the pressure regulator 302 also operates, supplying fuel from the branch pipes 38 and 39 as well. here,
When the engine is stopped, the solenoid 304 is driven, the diaphragm 305 is pulled down, and the branch pipes 32, 33,
Empty the fuel in 38 and 39. When starting, pull up the diaphragm 305 and connect the branch pipes 32, 33, 3.
8.39 is filled with fuel.

Next, atomization of fuel will be explained.

In the configuration shown in FIG.
The flow rate of fuel flowing out from the orifices 34a and the like at the tips of 8, 33, and 39 is generally low. Furthermore, when the orifice 34a is opened into the intake pipe 43, the fuel is sucked out by the suction negative pressure, and the pressure in the branch pipe 32 tends to fall below atmospheric pressure. In order to avoid this, as shown in FIG.
is provided upstream of the orifice 311. In this way, the outlet of orifice 34a is maintained at atmospheric pressure. The fuel flowing out from the orifice 34a is atomized by the auxiliary air in the passage 310 and supplied to the engine.
be done. Intake pipe 43 with throttle valve 41 fully open
When the pressure is close to atmospheric pressure, the auxiliary air passage 31
A compressor is provided upstream of the orifice 311 to increase the air flow rate through the orifice 311 and promote atomization. Also,
As shown in FIG. 11, there is a cylinder 312 inside the intake pipe 43.
This is made to resonate with a 20 to 30 kHz vibrator using a piezoelectric element 313, and a branch pipe 32 is installed on the inner surface of the cylinder 312.
Atomization of the fuel can be promoted by introducing the fuel into the fuel.

Therefore, according to this embodiment, in the distribution type fuel supply device, the fuel in the branch pipe is taken in and out of the branch pipe of the engine using the control valve for intake and discharge of fuel provided at the inlet of the branch pipe. fuel pressure
Even if it is as low as 0.6 kg/cm ² , problems caused by the generation of fuel vapor bubbles can be avoided, so the driving horsepower of the fuel pump can be reduced and the fuel consumption of the engine can be reduced.

As explained above, according to the present invention, generation of fuel vapor bubbles in fuel piping is prevented and fuel pressure is reduced.
It is possible to reduce the fuel pump drive horsepower to around 0.6Kg/cm ² .

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a detailed configuration diagram of a flow dividing section, Fig. 3 is a pressure characteristic diagram of fuel flow rate, Fig. 4 is a diagram showing the relationship between pressure and flow rate, and Fig. 5 is a diagram showing the relationship between pressure and flow rate. 6 is a diagram showing another embodiment of the flow divider, FIG. 7 is an explanatory diagram of the operation of the valve stem, FIG. 8 is a diagram showing a modification of FIG. 6, and FIG. The figure shows another embodiment of the flow divider, FIG. 10 is a configuration diagram of an orifice, and FIG. 11 is a diagram showing a vibrator provided in the intake pipe. 1...Fuel pump section, 2...Fuel metering section, 3...Diversion section, 4...Air metering section. 〓〓〓〓〓

Claims (1)

[Claims] 1. A fuel supply device in which fuel metered by one fuel metering valve is divided into a plurality of fuels through a branch pipe, and each of the divided fuels is distributed and supplied to a corresponding plurality of cylinders, The metering valve is a control valve for sucking and discharging fuel that operates in response to the start and stop of the engine, and substantially discharges the fuel in the branch pipe from the branch pipe when the engine is stopped, and fills the fuel into the branch pipe when the engine starts. A fuel supply device characterized in that it is provided at each branch pipe inlet of a downstream fuel passage.